Patent GB-340942-A (GB)
Title: Improvements in electrical driving gear
IPC: H02P5/695
Filed: 1929-10-02
Abstract: 340,942. Electromechanical power transmission systems. CAMPBELL & ISHERWOOD, Ltd., Raleigh Street Works, and ROTHWELL, S. R., 74, Merton Road, both in Bootle, near Liverpool. Oct. 2, 1929, No. 29796. [Classes 35 and 38 (iv).] Alternating current induction machines; mounting rotors. -A reversible variable speed drive, particularly adapted for winding gear, such as a ship's winch, comprises a primary motor, energized by direct current and generating alternating current or vice versa, and a transmission motor one element of which is coupled to the load and the other to the primary motor and the field winding of which is energized alternatively by direct current for a forward drive and by alternating current for reverse driving. In a modification the primary motor is an induction motor and the low periodicity slip currents are used for the field of the transmission motor in place of a direct current excitation. Speed variation may be obtained by a variable resistance in series with the armature of the primary motor, by regulating its shunt field or diverting a series field, or by resistances in a wound rotor of the transmission motor. The rotor of the transmission motor may have a squirrel-cage winding, and to give a torque under stalled conditions two windings may be provided, a high resistance winding with low impedance and a low resistance winding with high impedance, the current in the latter increasing as its periodicity falls. Fig. 1 shows diagrammatically a direct current primary motor M direct coupled to the field magnet A of the transmission motor the rotor B of which is secured on the load shaft D. Slip rings m<3>, t<3> are connected respectively to the armature of the motor M and field magnet A, the latter having a three-phase winding. A controller C connects the slip rings t<3> in series with a rheostat R across the D.C. supply, as shown, for driving in one direction, and to the slip rings m<3> for reverse driving. In the latter condition the direction of rotation of the field produced is opposite to that of the field magnet and the number of poles of the winding is so chosen to give a suitable nett speed in the reverse direction. Two-phase or multiphase currents may be used in place of the three-phase currents. The elements A and B may be interchanged in position. The primary motor M may be a rotary converted fed from A.C. mains. Fig. 6 shows the construction of a machine having a two-phase winding on the transmission member A. This member is carried by a wheel a<3> keyed to the shaft m<5> of the primary motor M and by a rotating member a<5> supported by a bearing a<6> on an end plate a<7> in which the driven shaft D is journalled. The end of the shaft D carrying the induction member B is supported in a bearing b<2> in the end of the shaft m<5>. An intermediate bearing plate a<10> carries the inner bearing of the shaft m<5>, the outer bearing m<11> being housed in the end of the primary motor casing m<15>. In an alternative construction the field magnets of the transmission motor are carried by a ring secured to a wheel keyed on the end of the shaft m<5>.